Analyzing the response distribution of DO concentration and its environmental factors under the influence of typhoon rain events with remote sensing

Typhoon rain events are important factors that trigger changes in dissolved oxygen concentrations in watersheds. The direction of the typhoon driving force is clear, but the mode of action and mechanism are complex. Moreover, quantifying the relationship between these actions and dissolved oxygen is challenging. This study collected measured data from water quality monitoring and remote sensing during the 2022 typhoon rain events. By analyzing the changes in typhoon driving factors and dissolved oxygen (DO) concentrations in water under various typhoon storms, extended MOORA plus the full multiplicative form (MULTIMOORA), Multiscale Geographic Weighted Regression (MGWR), and spatial autocorrelation analysis were used to evaluate the response of DO concentration. Furthermore, the effects of the atmospheric environment under the influence of human activities on the response distribution of the urban water environment were analyzed. The results of the study showed that under the effect of a typhoon with higher rainfall intensity, the response of DO concentration in the water body of the river in the center of the city was better. However, the response of DO concentration in the water body at the mouth of the sea had a tendency to become worse. Under the influence of typhoon rain events with smaller intensity, the scouring effect of rainwater dominated, and the DO concentration response in the water body had a tendency to become worse. The analysis of spatial heterogeneity under the influence of human activities showed that the ranking values of DO concentration response in rivers in the city area of Zhongshan, under the influence of typhoon rain events, were positively correlated with the distribution of ozone (O3) concentration and sulfur dioxide (SO2) concentration in the eastern, central, and western parts of Zhongshan. Conversely, it was negatively correlated with the distribution of O3 concentration and SO2 concentration in the northern and southern parts of Zhongshan. Based on the research results, we constructed a technique to evaluate the response of dissolved oxygen concentration during the typhoon transit period, which can provide an indicator reference for urban managers in water environment management

Changes in the Brain Microstructure of Children with Primary Monosymptomatic Nocturnal Enuresis: A Diffusion Tensor Imaging Study

Background: Primary monosymptomatic nocturnal enuresis (PMNE) is a common disorder in school-aged children. Previous studies have suggested that a developmental delay might play a role in the pathology of children with PMNE. However, microstructural abnormalities in the brains of these children have not been thoroughly investigated. Methodology/Principal Findings: In this work, we evaluated structural changes in the brains of children with PMNE using diffusion tensor imaging (DTI). Two groups consisting of 26 children with PMNE and 26 healthy controls were scanned using magnetic resonance DTI. The diffusion parameters of fractional anisotropy (FA) and mean diffusivity (MD) were subjected to whole-brain, voxel-wise group comparisons using statistical parametric mapping (SPM). When compared to healthy subjects, children with PMNE showed both a decrease in FA and an increase in MD in the thalamus. MD also increased in the frontal lobe, the anterior cingulate cortex and the insula; these areas are all involved in controlling micturition. The significant changes seen in the thalamus could affect both urine storage and arousal from sleep. Conclusions/Significance: The microstructure abnormalities were observed in the thalamus, the medial frontal gyrus, the anterior cingulate cortex and the insula, which are involved in micturition control network. This indicates developmenta

Preparation, Properties and Microstructure of Non-Calcination Rock Powder Brick with Orthogonal Experiments

In this paper, the preparation method and reasonable mix ratio of non-calcination brick with rock powder, cement, lime and fly ash ceramsite (FAC) as the raw materials were experimentally evaluated. To better understand the effects of each component on the performance of non-calcination rock powder brick (NCRPB), an orthogonal experimental design was conducted with the water–cement ratio (W/C), rock powder–cement ratio (R/C), lime content (wl) and FAC content (wf) as the main factors, which involved four factors and three factor levels. According to the orthogonal experimental design, the compressive strength, water resistance and bulk density of nine groups of NCRPB specimens were tested. The results show that R/C was the most important factor affecting the compressive strength and water resistance, while the FAC content influenced the bulk density of NCRPB greatly. In this study, the reasonable mix of W/C, R/C, wl, and wf in weight was 0.6, 3.0, 30% and 21%, respectively. In addition, the microstructure and strength formation mechanism of NCRPB were analyzed by using SEM and XRD. The test results show that the rock powder having pozzolanic activity could react with the additional Ca(OH)2 to produce hydration products, leading to the improvement of the performance of NCRPB

Effect of Nano-SiO₂/PVA Fiber on Sulfate Resistance of Cement Mortar Containing High-Volume Fly Ash

Sulfate resistance of high-volume fly ash/cement mortars hybrid containing 0~1.5 wt.% of nano-silica (Nano-SiO2, NS) and 0~1.0 vol.% of polyvinyl alcohol (PVA) fibers was investigated in this study. Fly ash was replaced with Portland cement at levels of 60% by weight. The resistance to sulfate attack was investigated by exposing the mortars to 10 wt.% sodium sulfate (Na2SO4) solutions for 72 days, after which change in mass, compressive, and flexural strengths were determined. For comparison, the compressive and flexural strengths of cement mortar after 100 days of curing in water were also investigated. Microstructural deteriorations caused by sulfate attack were analyzed by using scanning electron microscope (SEM). The test results showed that the combination of NS and PVA fibers was effective in enhancing the mechanical properties and the resistance to sulfate attack. After 28 days curing, the hybrid addition of 1.5 wt.% NS and 1.0 vol.% PVA fibers increased the flexural strength by 90% over the control one without NS and PVA fiber. Moreover, regardless of PVA fibers content, due to the crystal nucleus and pore-filling effects, the adding of 0.5 wt.% NS increased the compressive strength by 67.1~118.2%. Chemical reaction took place between fly ash and Na2SO4 as no un-hydration particles could be observed in the samples immersed in Na2SO4 solutions for 72 days, while a lot of un-hydration fly ash particles could be found in the SEM image of mortar after 100 days curing in water. The chemical reaction production could increase the adhesive property and fill the pores of cement mortar. As a result, the compressive and flexural strengths of cement mortars after immersed in Na2SO4 solution for 72 days, were much higher than that after 28 days curing. Moreover, the compressive strength of mortars incorporating 1.0~1.5 wt.% NS was even higher than that after 100 days curing in water, indicating the combination of Nano-SiO2/PVA fiber is effective in enhancing the resistance to sulfate attack

Effect of Nano-SiO2/PVA on Corrosion Behavior of Steel Rebar Embedded in High-Volume Fly Ash Mortar under Accelerated Chloride Attack

In this paper, the influence of Nano-silica (NS) and Polyvinyl alcohol (PVA) fibers on the corrosion behavior of steel rebar embedded in high-volume fly ash cement mortars under accelerated chloride attack was studied by using an impressed voltage technique. The PVA fibers used were 1.0 vol.%, and two mass fractions of cement (50 and 60 wt.%) were replaced by fly ash. Four NS mass fractions (0, 0.5, 1.0, and 1.5 wt.%) were utilized in this paper. In addition, the mono and hybrid effects of NS and PVA on the mechanical properties and water absorption of mortar were also studied. The results showed that the incorporation of PVA and nano-SiO2 can improve the flexural and compressive strengths of high-volume fly ash mortar. Generally, the flexural and compressive strengths increased with the increase of nano-SiO2 content. Moreover, the incorporation NS can also reduce the capillary water–absorption rate of cement mortar. The impressed voltage corrosion test indicated that the composite incorporation of nano-SiO2 and PVA can significantly delay the deterioration process of steel bars in mortar, effectively reducing the steel rebar’s corrosion level and increasing the exposure time of the surface crack. With hybrid-incorporation 1.0 vol.% PVA and 1.0 wt.% nano-SiO2, the steel rebar had the lowest corrosion degree, which exhibited a mass loss of 49% and increased the broken time by 71% as compared to the control mortar

Mechanical Properties and Microstructure of Polyvinyl Alcohol (PVA) Modified Cement Mortar

The mechanical properties of cement mortars with 0~2.0% (by mass) polyvinyl alcohol (PVA) were experimentally studied, and the effects of PVA incorporation on the hydration products and microstructure of the cement mortar were determined with differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the rational content of PVA formed evenly dispersed network-like thin films within the cement matrix, and these network-like films can bridge cracks in the cement matrix and improve the mechanical properties of the cement mortar. Over- incorporation of PVA may result in the formation of large piece polymer films that coat the cement particles, delay the hydration of the cement mortar and adversely affect its performance. The mechanical properties of the cement mortar show a significant increase and then decrease with a change in the PVA incorporation. When the PVA content was 0.6% and 1.0%, the mortar had the best compressive and flexural strengths, respectively. The compressive strength of the cement mortar increased by 12.15% for a PVA content of 0.6%, and the flexural strength of the cement mortar increased by 24.83% for a PVA content of 1.0%

Fully Automated and Robust Cable Tension Estimation of Wireless Sensor Networks System

Accurate estimation of cable tension is crucial for the structural health monitoring of cable-supported structures. Identifying the cable’s force from its vibration data is probably the most widely adopted method of cable tension estimation. According to string theory, the accuracy of estimated cable tension is highly related to identified modal parameters including natural frequencies and frequency order. To alleviate the factors that impact the accuracy of modal parameters when using the peak-picking method in wireless sensor networks, a fully automated and robust identifying method is proposed in this paper. This novel method was implemented on the Xnode wireless sensor system and validated with the data obtained from Jindo Bridge. The experiment results indicate that, through this method, the wireless sensor is able to distinguish the cognizable power spectrum, extract the peaks, eliminate false frequencies and determine frequency orders automatically to estimate cable tension force without any manual intervention or preprocessing. Meanwhile, the results of natural frequencies, corresponding orders and cable tension force obtained from the Xnode system show excellent agreement with the results obtained using the Matlab program method. This demonstrates the effectiveness and reliability of the Xnode estimation system. Furthermore, this method is also appropriate for other high-performance wireless sensor network systems to realize self-identification of cable in long-term monitoring

Modified recycled concrete aggregates for asphalt mixture using microbial calcite precipitation

Using recycled concrete aggregate (RCA) in an asphalt mixture has many economic and environmental benefits for our society. However, due to the poor adhesion of RCA to asphalt binder, the replacement of normal aggregate with RCA leads to a reduction in the properties of asphalt mixture. This study presents a new approach to overcome this deficiency by treating RCA with microbial carbonate precipitation to develop chemical bonds between RCA and asphalt binder. This study first investigates the effect of this surface treatment on the properties of RCA. The experimental results showed that the capillary water absorption and porosity of the treated-RCA could be reduced by 86.5% and 32%, respectively, as compared to those of the untreated-RCA. In addition, this study investigates the influence of this surface treatment on the interfacial behavior of RCA to asphalt binder by means of standard boiling test and direct tension test. According to the test results, the adhesion behavior of the treated-RCA to asphalt binder could be improved by 2 grades as compared to the asphalt mixture with untreated-RCA. Moreover, the bonding strength of treated-RCA to asphalt binder was also improved by 55%. The formation of chemical affinity between treated-RCA and asphalt binder, as shown in FTIR spectra, is the explanation for the enhancement in the bonding strength and water susceptibility for the treated-RCA-asphalt mixture